They work good when they work. My D-8 air conditioner went on the fritz today. Yeah yeah, air condition in the middle of winter you say!! It get plenty hot in the cab with all of that glass. I'll run the air just about all of the time. I had to open the side glass and it was getting dusty inside pretty quick. I hate that too. I like to keep it clean inside. Do you have very much of that red rocky dirt up there? We have a lot here and some of it is flint rock and gets sharp as razor blades sometimes. I think I only have a few more weeks on the dozer and then I'm back on a blade. Hey I might have to learn all over hahaha..
I run the AC compressor all the time, regardless of temps. Keeps the humidity down in the cab to help with window fogging.
Our dirt is either Missouri Clay or black top soil. Mostly clay. Sometimes our quarries will get into a thin layer of flint rock in their pit. Everyone complains when that happens because as you said it splinters very sharp. People start having a lot of flat tires from driving on it.